GB337464A - An electrically controlled variable speed-gear - Google Patents

Abstract

337,464. Casson, W., and Roberts, H. Aug. 3, 1929. Electromagnetic clutches.-The invention relates to power transmission devices comprising a dynamo-electric machine having an armature and field magnet, one of these elements being connected to the driving shaft and the other to the driven member, means being provided to vary the magnetic flux so as to vary the power transmitted. According to the invention, epicyclic gearing serving as a driving connection between the driving shaft and the dynamo-electric element not coupled to the driven shaft is such that when the driven shaft element is stationary or rotating at low speed, the first mentioned dynamo-electric element is driven in the opposite direction to the driving shaft. The Figure shows a machine of the continuous-current series generator type in which the field magnet 15 which is rigidly connected to the driven shaft 10 carries differential field windings 20, 21 which are directly connected to the commutator brush 17 on one side and connected separately at their other ends through rheostats 31, 32 to the fixed casing 11 which is in electrical connection with the other commutator brush 18. The driving shaft 1 carries a sun pinion 2 which meshes with planet pinions 3. The, pinions 3 mesh with complementary pinions 3a engaging with a sun pinion 4 on the armature shaft. The spindles 5 of the planet pinions 3, 3a are mounted in a housing 6 fixed to the magnet yoke casing 7. In operation, when the field magnet is held, the armature will rotate in the opposite direction to the driving shaft 1. The fluxes set up by the current generated tend to cause the armature and field to rotate together so that on light loads the two members rotate in the same direction as the driving shaft. As the load on the shaft 10 increases and the field member slows down, the armature also slows down, stops and finally reverses its direction of rotation. In a modification, the armature carries a squirrel cage winding and the field member a single exciting winding fed from a separate source. Continuous current from an external source may be fed to the field magnet winding or to an auxiliary field winding in the arrangement shown in Fig. 1. A number of transmission units may be employed in combination, the driven shaft of the first being connected to the driving shaft of the next unit.